Simulated brushed cymbal tone generating system for electronic organs



Wl MUNCH, JR ED CYMBAL TONE GENERATING SYST FOR ELECTRONIC ORGANS June 23, 1910 SIMULATED BRUSH Filed Oct. 22, 1965 R w S mw m N R EU 0 W; m mM 5516:? Bu Q :25 $22 =2 355:3. zwzum Eowo ml n W l 3 w w .v 4(37-(2 I 8 MN PN bu 20. 0U mu 7 Jlvu 5i NH om d K62. mg NE. soon EUZZ s :5

United States Patent 3,516,319 SIMULATED BRUSHED CYMBAL TONE GENERAT- ING SYSTEM FOR ELECTRONIC ORGANS Walter Munch, Jr., Park Hills, Ky., assignor to H. Baldwin Company, Cincinnati, Ohio, a corporation of Ohio Filed Oct. 22, 1965, Ser. No. 502,011 Int. Cl. Gh 1/02, 5/12 US. Cl. 841.05 21 Claims ABSTRACT OF THE DISCLOSURE The present invention relates generally to electric organs and more particularly to systems for generating sounds simulating those produced by a cymbal struck by a brush.

It is desirable that electric Organs have a facility for generating brushed cymbal sounds, in order that the usual musical tones .provided by the organ may be accomplished by a rhythm beat. In accordance with the present invention, a system is provided for generating two diverse brushed cymbal sounds, one in response to actuation of pedal keys and the other in response to manual keys. The pedal brush is arranged to continue as long as a pedal key is held down, and to include a sustain thereafter. The manual brush has a short decay and is pulsed only as a manual key is struck, to simulate the sound of a cymbal which is struck and then muted. The two sounds can be produced concurrently, and the manual brush can be then identified with the pedal brush still sounding. The brush generators may be used either with or without other organ stops. Since two diverse brush sounds must be available, separate control circuits are provided for each, which are operative disjunctively or conjunctively to control the some tone source, i.e., a self quenched super-regenerative oscillating detector. The brush sound is filtered, prior to application to an audio output system, to remove the detector carrier (2 m c.) and most of the squelch fre quency, in order to avoid overloading the audio output, especially in the presence of conventional tone, and thus produce distortion.

The tone source for the brush sound is a transistorized random noise generator which operates as a self-quenching superregenerative detector. In the absence of signal, thermal noise starts the oscillations, which are then selfquenched by build-up of a bias. When the oscillations cease the bias leaks off, whereupon oscillations are again started 'by thermal noise. Since the thermal noise is random in nature, oscillations will start at random times and have random amplitudes, which produces a characteristic hiss in the tone output.

The superregenerative oscillator operates at about 2 mo. and the squelch frequency is between 20 kc. and 30 kc., i.e. is supersonic.

The brush generator is triggered from switch headers, i.e. in response to tones, and specifically the 8' triangular waves are used for brush pedal and the 4 square waves for manual brush.

The pedal brush operates as long as the pedal key is activated. In the case of the manual key, only a pulse of output is produced, as a key is struck, and the key must be released and that or another key struck to produce a succeeding tone.

Patented June 23, 1970 lCC It is, accordingly, a broad object of the invention to provide a system for simulating the sound of a, brushed cymbal.

It is another object of the invention to provide a system for simulating the sound of a cymbal which is muted after being struck by a brush.

A further object of the invention resides in the provision of a system for generating conjunctively or individually the sounds of a sustained cymbal and of a cymbal which is muted after being struck, both sounds deriving from a common source oscillator.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of one specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein the single figure of the drawings is a circuit diagram of a system according to the invention.

Referring now to the accompanying drawings, terminal 10 is connected to the 8 triangular waveform pedal collector of an electric organ, not shown, and terminal 11 to the 4 square waveform manual collector.

Tone appearing at terminal 10 is applied via capacitor C and resistance R in series, to the base of transistor TR The latter operates as a conventional amplifier, transferring signal to the base of transistor TR A capacitor C is connected from the collector of transistor TR to ground, and the transistor has a grounded emitter and its collector is loaded by resistance R The base of transistor TR is connected to ground via resistance R and no external bias is provided, so that transistor TR is biased to operate as a detector, and is normally at cutoff. The capacitor C is normally charged towards the potential of voltage supply line 12, causing transistor TR to conduct heavily. When detector TR conducts, it reduces the charge on capacitor C and this reduction subsists while tone exists at terminal 10. Capacitor C forms a bias source for transistor TR and the reduction of voltage cuts off TR raising its collector voltage from ground value to near line value (16 v.). That voltage proceeds via diode D and line 14 to ground, via normally closed pedal brush switch S But if the latter is open, current will fiow through D R D R to ground. The voltage across R will bias transistor TR suificiently conductive to pass signal in line 15, with amplification of the signal.

Transistor TR has a collector load R and an emitter bias resistance R and capacitor C In addition, a carrier bypass capacitor C is connected between base and emitter. The DC voltage on line 15 then acts as a gating voltage to render both diode D and transistor TR conductive. Capacitor C and R form a bias network to stabilize the operating point of transistor TR when the gate is turned on.

When pedal signal is removed from terminal 10, TR will become conductive, thus removing its collector voltage. However, the then voltage across capacitor C is blocked at diode D and charge must leak oif slowly through R D and R providing a sustain effect after the pedal key is released.

In the manual control circuit, operation of transistors TR TR and capacitor C is precisely analogous to that of transistor TR TR and capacitor C in the pedal control circuit. Transistors TR and TR form a bistable circuit. Under quiescent condition TR is cut off. Transistor TR will then conduct since the collector of transistor TR then provides the base of transistor TR with high positive potential. The emitters of transistors TR and TR, have a common resistance to ground, R while the base of TR is connected directly to the collector of TR It follows that TR when conductive holds TR7 nonconductive. When a signal is applied to terminal 11, the voltage across capacitor C decreases, driving TR toward cut off, and causing TR7 to conduct, which in turn raises the emitter voltage of TR accentuating the cut-off. The voltage at the collector of transistor TRq decreases sharply, causing a short negative-going DC pulse to pass through series capacitor C Only one short pulse can pass, in response to tone initiation, regardless of the duration of the tone, and this pulse is transferred to the base of transistor TR Transistor TR has a grounded emitter, and its collector and base are connected to positive voltage line 12, which maintains TR normally conductive. Accrual at the base of TR of a negatively going pulse cuts off TR and causes a high positive voltage to appear at its collector. This voltage is transferred via diode D to lead 18, and, when switch S is open, to diode D as a pulse of positive voltage, which renders diode D conductive and effects transfer of signal from super-regenerative oscillating detector D to gate TR and also effects transfer of bias to the base of transistor TR to render the latter conductive.

Accordingly, diode D and transistor TR serve as double or cascade gates for manual brush tones, as well as for pedal brush tones.

After the initial voltage has passed through capacitor C the latter will charge through resistances R and R until transistor TR again becomes conductive, lowering the collector voltage of transistor TR However, the charge on capacitor C connected to the cathode of diode D cannot decrease through diode D but leaks off through resistance R diode D and resistance R which are selected to provide a very short sustain. After capacitor C is charged and capacitor C has discharged gate diode D remains non-conductive regardless of how long the key is held down, since capacitor C can transfer only a change in voltage, which can occur only after the manual key is released and thereafter depressed. The manual brush shound thus occurs only on initiation of a tone called forth by a manual key. Release of the manual key causes the collector of transistor T R to rise, there being no longer a discharge path for capacitor C which then causes transistor TR to conduct and transistor TR'] to be cut off, to restore quiescent conditions.

The source of tone is a superregenerative oscillator or detector D of the self-quenching type. Oscillator or detector D includes a transistor TR having an inductance T connected from end tap A to the base of transistor TR via capacitor C Mid tap C of inductance T is connected to the emitter of transistor TR and its collector is connected directly to voltage supply lead 12. Resistance R provides bias for the base of TR and a tuning capacitor C is connected in series with capacitor C between taps A and B. The oscillator or detector D oscillates normally at 2 mc., but is tunable by varying a slug in inductance T Resistor R connected between outer taps A and C, lowers the Q of the resonant circuit to below 55.

Thermal noise exists across resistance R and the oscillator is arranged to have its oscillations start in response to this noise from a quiescent condition.

A superregenerative detector is essentially an oscillating detector in which the oscillating transistor or tube is alternated between oscillating and non-oscillating conditions; and for the latter purpose a squelch circuit, including a squelch capacitor, is provided. Assuming the latter to provide a high enough bias the transistor TR achieves oscillatory condition. Oscillations then proceed to buildup, being started by a pulse of thermal noise occurring while the system is just at the point of oscillating. As oscillations build up, the voltage across squelch capacitor C increases, until eventually the decay is sufficient to cut off the oscillator, i.e. to render the oscillator non-oscillating. When this occurs the charge on the squelch capacitor C decreases until the oscillator again becomes oscillatory, when the cycle repeats. Thermal noise, in the system of the invention, operates as does a signal to be detected in a superregenerative radio receiver. Since the noise is random in time and amplitude, initiations of oscillation will be random in time and the maximum buildup of oscillations will be random in amplitude. The squelch frequency for the present system is supersonic, i.e., between 20 kc. and 30 kc. The capacitor C which is the squelch capacitor of the oscillator, acts also as a bypass for oscillator frequency, at 2 mc. Squelch frequency is partially determined by values of resistance R and capacitance of capacitor C which provides with the capacitance of C an RC time constant, and by the value of beta of transistor TR which modifies the RC time constant.

superregenerative detectors have long been known to produce a characteristic hiss in the absence of signal other than thermal noise, the hiss being amplified thermal noise, but the amplification being logarithmic rather than linear, which serves to suppress noise pulses of large amplitude and which introduces an amplitude-limiting action. This action constitutes one of the valuable characteristics of the superregenerative noise detector as a source of audio noise, but additional thereto is the fact that noise occurs at near a fixed super audible rate, which is not, however, regular in frequency nor uniform in amplitude. The noise provided by the present system is at high level, and has a regularlity of character and a superposed randomness, which is musically pleasing and desirable.

The signal at tap C is divided by resistances R R the junction of which is connected via capacitor C 10 the anode of gate diode D Capacitor C assures that only AC signal will appear at the anode of gate diode D Gate transistor TR when conductive, passes signal via capacitor C to a pi filter F composed of shunt elements C C and a series component consisting of inductance L, and capacitor C in shunt thereto. The output of the filter is passed to a pedal pre-amplifier terminal via a volume control potentiometer R and series capacitor C21.

Capacitor C at the input of gate transistor TR acts as a bypass for 2 mc. carrier, while filter F acts as a tone forming filter for audio frequencies, eliminating most of the squelch frequency. Capacitor C acts to prevent 2 me. carrier leaking into the power lead 12, by grounding the power lead 12 and the collector of transistor TR for carrier frequency.

Assuming that a pedal tone gating signal is applied to lead 15, and that during that pedal tone, a manual tone gating signal is applied to lead 15, the neat voltage appearing across resistance R will increase, increasing the bias on the base of transistor TR and therefore increasing its gain. The total signal at the output of the composite gate D "PR deriving from the single tone source D, is then distinguishable for conditions (a) switches S and S open, (b) switch S open or (c) switch S open, and both output tones can be recognized, even when in superposition.

While I have described and illustrated one specific embodiment of my invention, it will be clear that variations of the details of construction which are specifically illustrated and described may be resorted to without departing from the true spirit and scope of the invention as defined in the appended claims.

What I claim is:

1. A gate circuit for a single source of tone signal, comprising a diode circuit in cascade with said single source of tone signal,

an amplifier in cascade with said diode circuit,

means normally maintaining said amplifier substantially a first source of gating current,

a second source of gating current,

a resistance arranged to provide on-bias for said amplifier, and

means for selectively passing said gating currents simultaneously and individually through said resistance.

2. The combination according to claim 1 wherein said last means includes means for passing said gating current simultaneously and individually through said resistance via said diode circuit.

3. The combination according to claim 2 wherein said diode circuit includes a single diode,

a load resistance to ground connected in series with said single diode,

said amplifier including a transistor having a base,

an emitter and a collector,

shunt means in series with said emitter for self-biasing said transistor,

the cathode of said single diode being directly connected to said base, and

a resistance load for said collector.

4. In a control circuit for musical tone signals having initial points and termination points,

a terminal to which said tone signals are applied,

a detector in cascade with said terminal,

a capacitor,

means normally maintaining said capacitor charged,

means responsive to said tones for discharging said capacitor through said detector,

a bistable circuit including two bistably cross coupled transistors,

means connecting said capacitor to one of said transistors as a bias voltage source maintaining said transistor conductive while said capacitor is charged, whereby the other of said transistors is maintained nonconductive and said bistable circuit is in one state,

discharge of said capacitor reducing said bias voltage and transferring said bistable circuit to an alternate state,

means responsive to transfer of said bistable circuit to said alternate state for generating a single short pulse of voltage,

a source of tone,

an output circuit, and

means responsive to said short pulse of voltage for transferring signal from said source of tone to said output circuit.

5. In a control circuit,

a transistor,

means normally maintaining said transistor non-conductive,

a capacitor connected across said transistor,

a resistance in series with said transistor, whereby the voltage across said capacitor decreases when said transistor is supplied with AC control signal,

a source of said AC control signal connected in controlling relation to said transistor,

a further transistor,

means connecting said capacitor in bias relation to said further transistor, said further transistor being normally conductive and being rendered non-conductive on decrease of voltage across said capacitor,

a diode,

a further capacitor,

means connecting said further capacitor and said diode in series with each other and in cascade with said further transistor, and

a slow discharge path for said further capacitor.

6. In a control circuit for gating a tone signal through to an output,

means responsive to said tone signal for providing a relatively high DC voltage and responsive to absence of said tone signal for reducing said DC voltage,

a diode conductive in the direction of said voltage,

a capacitor in series with said diode,

means connecting said diode and said capacitor to be responsive to said DC voltage, whereby said capacitor is charged via said diode in response to said tone signal and is restrained from discharge through said diode in absence of said tone signal,

a gate for said signal, and

means connecting said capacitor to said gate in bias relation to said gate.

7. In an electric organ,

a source of pedal tones,

a source of manual tones,

a first lead,

a second lead,

means responsive to said pedal tones for generating pedal gating voltage on said first lead for at least the duration of each of said pedal tones,

means responsive to said manual tones for generating a short manual gating pulse on said second lead in response only to initiation of each of said manual tones,

a normally non-conductive gate,

means connecting said leads in control relation to said gate for rendering said gate conductive in response to said gating voltages, and

means for at will grounding each of said leads.

8. The combination according to claim 7, wherein is provided circuit means for isolating each of said leads from the other of said leads to effectively prevent cross coupling therebetween.

9. The combination according to claim 8, wherein said leads are connected to a common point of said single gate via said circuit means for isolating.

10. The combination according to claim 9, wherein said means responsive to at least one of said tones includes a sustain capacitor, a diode, and means for charging said capacitor via said diode in response to said one of each tones, and means connecting one of said leads to said capacitor.

11. In an electric organ,

a source of pedal tones,

a souhce of manual tones,

a first lead,

a second lead,

means responsive to said pedal tones for generating pedal gating voltage on said first lead for at least the duration of said pedal tones,

means responsive to said manual tones for generating a short manual gating pulse voltage on said second lead in response only to initiation of each of said manual tones,

normally non-conductive gating means, and

means connecting said leads in control relation to said gating means for rendering said gating means conductive in response to said gating voltages.

12. The combination according to claim 11, wherein said gating means is a single gate.

13. The combination according to claim 12 wherein is provided circuit means for isolating each of said leads from the other of said leads to eifectively prevent cross coupling therebetween.

14. The combination according to claim 13, wherein said leads are connected to a common point of said single gate via said circuit means for isolating.

15. The combination according to claim 11 wherein said means responsive to one of said tones includes a sustain capacitor, a diode, and means for charging said sustain capacitor via said diode in response to said one of said tones, and means connecting one of said leads to said capacitor.

16. In an electronic organ,

a first keyboard,

a second keyboard,

first circuit means for deriving first tone signals in response to manipulation of said first keyboard, second circuit means for deriving second tone signals in response to manipulation of said second keyboard,

a noise signal source,

a gate means coupled in cascade with said noise signal source and having a control signal input means,

a first trigger circuit coupled between said first circuit means and said control signal input means,

a second trigger circuit coupled between said second circuit means and said control signal input means,

a tone filter coupled to said gate circuit, and

an output system coupled to said filter.

17. The combination according to claim 16, wherein said first trigger circuit includes means for maintaining said gate means conductive of said noise signal so long as said first tone signals exist, and

wherein said second trigger circuit includes means for rendering said gate circuit conductive of said noise signal only transiently in response to said manipulation of said second keyboard regardless of the duration of said manipulation of said second keyboard.

18. An electronic organ having at least one manual keyboard, a pedal keyboard, first circuit means for deriving manual signals from said manual keyboard, and second circuit means for deriving pedal signals from said pedal keyboard, the combination comprising:

a noise source,

a gate circuit coupled to said noise source and having a first input point and a second input point,

a first trigger circuit coupled between said first circuit means and said first input point,

a second trigger circuit coupled between said second circuit means and said second input point,

a tone filter coupled to said gate circuit, and an output system coupled to said filter.

19. The combination according to claim 18, wherein said first trigger circuit includes:

means for maintaining in said output system signal from said noise source via said gate circuit so long as pedal signal exists, and said second trigger circuit includes:

means for producing in said output system a transient signal from said noise source via said gate circuit when manual signal occurs.

20. In an electronic organ,

a first array of keys,

a second array of keys distinct from said first array of keys,

a first lead,

a second lead,

means responsive to actuation of any of said first array of keys for generating a first gating voltage on said first lead for at least one duration,

means responsive to actuation of any of said second array of keys for generating a second gating voltage on said second lead for a time audibly shorter than said duration and in response only to initiation of the last named actuation,

a normally non-conductive gating means, and

means connecting said leads in control relation to said gating means for rendering said gating means conductive in response to either or both of said gating pulses.

21. In a musical instrument,

means for calling forth a musical tone,

a first capacitor,

means responsive to operation of said last named means for passing only a transient current through said first capacitor regardless of the duration of said tone,

a diode,

a sustain capacitor,

means responsive to said current for transiently charging said sustain capacitor via said diode,

a source of tone signal,

said source of tone signal being arranged and adapted to provide a tone signal having an amplitude which is a direct function of a control voltage, and

means applying the voltage of said sustain capacitor to said source of tone signal as said control voltage, said source of tone signal including a relatively high resistance for discharging said sustain capacitor with a musically long time constant.

References Cited UNITED STATES PATENTS 3,140,336 7/1964 Campbell 84-1.0 3 3,244,938 4/1966 Schatz 307-246 X 3,328,506 6/1967 Park 84-126 X 3,291,886 12/1966 Tinker, 84-126 X 3,309,454 3/1967 Cutler et al. 84-126 X WARR EN E. RAY, Primary Examiner s. c1. X.R. 84-].08, 1.13, 1.17, 1.24, 1126; 307 243, 246, 259 

